Bumper jack and fluid system



I. V. K. HOTT BUMPER JACK AND FLUID SYSTEM March 14, 1961 6 Sheets-Sheet 1 Filed Jan. 18, 1955 INVENTOR. ION MK HOTT BY 5 3 3 5 March 14, 1961 v. K. HOTT BUMPER JACK AND FLUID SYSTEM 6 Sheets-Sheet 2 Filed Jan. 18, 1955 8 flw .m M 6 4. MM an 5 M 3 Y /s4 B /5a INVENTOR H/S ATTOENE VS /0/\/ l/ K HOTT I. V. K. HOTT BUMPER JACK AND FLUID SYSTEM March 14, 1961 Filed Jan. 18, 1955 6 Sheets-Sheet 3 lull INVENTOR.

ION l K HOTT BY WQW March 14, 1961 I. v. K. HOTT 2,974,490

BUMPER JACK AND FLUID SYSTEM Filed Jan. 18, 1955 s Sheets-Sheet 4' March 14, 1961 v. K. HOTT BUMPER JACK AND FLUID SYSTEM 6 Sheets-Sheet 5 Filed Jan. 18, 1955 JIE 1:7

INVENTOR.

BY W

March 14, 1961 I. v. K. HOTT 2,974,490

BUMPER JACK AND FLUID SYSTEM Filed Jan. 18, 1955 6 Sheets-Sheet 6 H i a l I i i i 1 I 1 HIS ATTORNEY-S 2,974,490 BUMPER JACK AND i Lun) SYSTEM Ion V. K. Hott, DaytomOhio; assignor to The Joyce- Cridland Company, Dayton, Ohio, a corporation of Ohio riled Jan. 18, 195"5, 'sa. No. 482,506

2 Claims. (Cl. 60 -52) This invention relates to an improved lifting jack particularly of the portable type, which. may be rolled into position beneath the load to be lifted.

It is among the objects of the present invention to provide a portable lifting jack having a base upon which the lifting unit is mounted, said lifting unit being actuated by hydraulic pressure to raise a load. The hydraulic pressure is provided by a fluid pump, actuated by an air motor, both pump and air motor being carried by said base which has casters attached thereto for permitting the jack to be rolled from one position into another.

A further object of the present invention is to provide a hydraulically actuated lifting jack of the type aforedescribed, in which air pressure is applied upon the fluid within the jack for causing the lifting unit quickly to be moved from full retarded position into the load engaging position. This air pressure upon the fluid in the jack also supercharges the fluid displacement chamber of the fluid pump and thereby increases its efiictency.

A still further object of the present invention is to provide the portable lifting jack as aforedescribed, with a manually actuated fluid pump, also carried by the base, said pump being operative to provide fluid pressure for actuating the lifting unit in case air pressure for operating the air pump is not available.

Other objects and advantages reside in the construction of parts, the combination thereof and the mode of operation, which will become more apparent from the following description.

These objects are accomplished by providing a lifting jack with a rigid frame or base to which rollers are attached for permitting the jack to be rolled upon the floor into any desired position. Some of these rollers are in the form of casters, swivelly secured to the base, While others are spring supported upon said base and normally hold the base ofi the floor when no load is engaged by the jack. The base, when a load is applied to the jack, is moved relatively to the spring supported rollers and into immovable engagement with the floor, thereby'preventing shifting of the jack on the floor while a load is being lifted or supported 'by the jack.

Two spaced, upright stanchions are rigidly supported by the base, said stanchions forming a slideway for the load engaging and lifting frame of the jack, said frame having rollers engaging the stanchions. The lifting frame has an angular bracket member extending therefrom, substantially parallel with the 'base. The bracket has a saddle-shaped, load engaging element secured at its outer ends.

The lifting unit, carried by the base, consists of two,

' concentric tubular members forming an annular chamber therebetween, which is the fluid supply reservoir. The inner tubular member is the working cylinder and contains a piston having a rod errtending therefrom, outside cylinder and attachedio the" c1oss'haddf the lifting frame.

r 2,974,490 Patented Mar. 14, 1961 A reciprocating, double acting fluid pump is carried by the base, said pump being operatively connected with an air motor, the air motor and fluid pump being constructed as a unit. A conduit connecting the air motor and the interior of the fluid reservoir above the level of the fluid therein, is connectible with any suitable source of air pressure. A block, interposed between the base and the fluid pump and lifting unit, provides 'valve controlled fluid passages connecting the two fluid displacement chambers of the double acting fluid pump with the fluid reservoir and the working cylinder respectively. A manually controlled fluid exhaust valve is provided in conduits connecting the working cylinder and fluid reservoir, said exhaust valve beingoperative to permit fluid to flow from the cylinder into the reservoir for purposes of lowering the jack supported load.

7 In order to render the jack usable in case of an air pressure failure or in the absence of an air pressure supply, a manually operative fluid pressure pump is carried by the base, the fluid displacement chamber of this pump being connected to the fluid reservoir and the working cylinder by valve controlled passages in the block.

When the air pressure supply is operatively connected to the fluid reservoir, above the level of the fluid therein, and with the air motor, the fluid within the reser voir will be forced through valved passages in the block, into and through the fluid displacement chambers of both power and hand operated fluid pumps, through other valved passages in the block and into the working cylinder, causing the piston therein to be actuated to move the lifting frame into load engagement with a substan tially fast and continuous movement. This air pressure upon the fluid is not suihciently high to cause the lifting frame to raise the load. The air pressure applied to the air motor will render it active to operate the double acting pump, the fluid displacement chambers of which are supercharged by the air pressured fluid there in. As the fluid displacement piston within the double acting pump is actuated by the air motor, a fluid pressure impulse will be delivered by the pump for each stroke thereof, said impulses being directed to the working cylinder and causing the piston therein to be raised to lift the load by actuation of the lifting frame con nected to said piston. The air pressure is shut off when the load has been raised to the desired height, thereby rendering the air motor inactive and consequently the ump driven thereby. v To lower the load, the exhaust valve controlling the spindle is actuated to permit the exhaust valve to be opened by fluid pressure, thereby permitting the fluid within the working cylinder to return to the reservoir and thus permit the piston within the working cylinder to be moved toward its lower position by the load.

In the drawings:

Figure l is a perspective view of the jack;

Figure 2 is a detail sectional View showing the fluid reservoir, working cylinder, the hand controlled fluid pressure exhaust valve and associated fluid passages;

Figure 3 is a detail view showing the hand operated fluid pump and its valve controlled fluid passages;

Figure 4 is a fragmentary, sectional view, taking along the line 1 -4 of Figure 3, showing the pressure limiting valve of hand actuated fluid pump;

Figure 5 is a side view, partly in section, illustrating the unitary air motor and fluid pressure pump;

Figure '6 is *1 fragmentary, sectional view showing the fluid flow control valves in fluid passages communicating with the lower displacement chamber of the power actuated fluid pressur pump illustrated in Figure 5;

Figure 7 is adetail top view of the fluid passage block.

portable lifting upon which the working cylinder and associated fluid reservoir and the fluid pressure pump are mounted;

Figure 8 is a detail sectional view taken along the line and in the direction of the arrows 8-8 in Figure 7;

Figure 9 is a sectional view taken in the direction of the arrows of line 99 in Figure 7;

Figure 10 is a section taken along the line 10-40 in Figure 7;

Figure 11 is a section taken along the line 11-11 in Figure 7;

Figure 12 is a section taken along line 12-12 of Figure Figure 13 is a section taken along line 1313 of Figure Figure 14 is a section taken along line 1414 of Figure 7;

Figure 15 is a section taken in the direction of the arrows of line 1515 in Figure 7;

Figure 16 is a diagrammatic view showing the fluid reservoir, the working cylinder, the power actuated fluid pressure pump and its driving air motor, the hand actuated fluid pressure pump, the hand controlled fluid pressure exhaust valve and all of the valve controlled fluid passages interconnecting them; and

Figure 17 is a fragmentary cross sectional view of a saddle-shaped rest.

Referring to Figure 1 of the drawings, the base 20 is shown equipped with swivelled rollers or casters 21 and a roller 22 movably attached to the frame or base 20 and ;yieldably held in normal position by a spring 23. The

cross bar 24 is normally held off the floor by the roller '22. However, when a load is engaged by the jack, spring 23 is overcome, permitting the base 20 and its cross bar 24 to move downwardly relatively to said roller 22, the cross bar coming to rest upon the floor and thereby hold the basc immovable on the floor under the influence of the load. Two spaced stanchions 25 and 26 are secured to base 20 and are rigidly held in upright position thereon by struts 27. These stanchions form a slide way for rollers 28 attached to opposite side members 29 and 30 of the lifting frame, the upper ends of which are secured together by the cross head 31.

The lifting frame has a bracket 32 extending angularly therefrom and substantially parallel with the base 20. A cross bar 33 is integral with the outer end of bracket 32. A saddle-shaped rest 35 is carried at the outer ends of the cross bar 33. The saddle-shaped rest is a load support that is turnable and lockable in two positions. These rests are adjustable into one position to engage a cross member of the load to be lifted, viz., the bumper of a vehicle, or into another position to engage another member of the load to be lifted, viz., the frame member of the vehicle. A transverse pin 35a extends through the sleeve portion of the saddle-shaped rest 35. The pin 35a rests in one of the slots 34a located in the upwardly directed stub shaft 34b carried by the cross bar 33.

The lifting frame, consisting of side members 29 and 30 and the cross head 31, is moved upwardly along the stanchions 25 and 26 by the work unit 40, detachably shown in Figure 2 and in Figures 1 and 3. All these figures show the work unit attached to a block 41, which, in turn, is secured to the base 20. Referring particularly to Figure 2, the work unit is shown consisting of two concentric tubular members 42 and 43, the latter being the larger in diameter to form an annular chamber or fluid reservoir 44. The tubular member 42, which is the smaller one, forms the working cylinder and is exteriorly threaded at both ends, the one being received by a threaded recess 39 in block 41, the other by a cover and spacer cap 45, having a central opening provided with a sealing ring 46. The larger, outer tubular member or reservoir shell 43 sealingly engages both the block 41 and the cap 45, and is held concentric with the cylinder 42 by said block and cap. A piston rod 47, predeterminately less in diameter than the inside of cylinder 42, slidably extends through the sealed opening in cap 45 and at its inner end has a composite piston 48 attached thereto, said piston consisting of a fibrous washer 49 clamped to the piston rod 47 by a bolt 50. The outer end of the piston rod 47 is attached to the cross head 31 of the lifting frame consisting of side members 29 and 30 and the angular bracket 32. Cap 45 has a passage 55 providing communication between the upper ends of the cylinder 42 and the fluid reservoir 44. An orifice 42 is provided in the wall of the cylinder 42 at a distance from the upper end of the cylinder suflicient to be cleared by the piston 48 when in its extreme uppermost position, thereby providing pressure relieving communication between the cylinder chamber beneath the piston and the fluid reservoir.

Block 41 may be defined as the conduit block having the various fluid passages or conduits and control valves providing communication between the several operating units of the device. As shown in Figures 2 and 122, block 41 has two horizontal passages 51 and 52, one directly beneath the other, said passages being drilled or bored from the one outside surface of the block, the passage 51 terminating directly in the lower end of the working cylinder 42'. Passage 52 communicates with a vertical passage 53, terminating in a filtering element 54 inside the fluid reservoir 44. The outer ends of passages 51 and 52 are closed by plugs 55. Another vertical passage 56, drilled from the upper surface of block 41, communicates with passage 52 and terminates in passage 51, thus providing communication between said passages 52 and 51. As shown in Figures 2 and 12, passage 56 has areas of different diameters, the larger, outer end area being interiorly threaded to receive an interiorly threaded nipple 57, as shown in Figure 2. The portion of passages 56 between passages 51 and 52 has a valve seat 58 for the ball check valve 59, which is maintained in passage closing engagement with seat 58, to prevent fluid flow from passage 51 into passage 52, by the manually operated spindle 60 threadedly engaging the nipple 57 and supported in the stationary rubber grommet 61 and having a hand wheel 62 attached at its upper end. This spindle 60 may be operated to release the ball check valve 59 for permitting fluid pressure discharge from passage 51 to passage 52, or may be operated as shown in Figure 2, to engage and press valve 59 to close passage 56 and thus prevent fluid flow from passage 51 to passage 52. Figure 2 shows the spindle 60 attached to a coupling 63, which is also secured to the stem 64 having a portion threadedly received by the nipple 57 and extending into passage 56, so as to be engageable with the ball check valve 59.

Another operating unit 70 of the jack of the present invention comprises the double acting, reciprocating fluid pump and air motor carried by and attached to the block 41. As shown in Figure 5, the reciprocating pump portion of this unit 70 consists of a cylinder block 71 mounted upon the block 41 with sealing elements therebetween. A central opening longitudinally of block 71 forms a portion of the pump cylinder 72 in which the pump piston 73 reciprocates. A recess 74 in block 41. predeterminately larger in diameter than the piston 73. aligns with the cylinder 72 and forms the lower fluid displacement chamber of the double acting pump. A sealing collar 66 is housed in an enlarged recess in block 71. said collar 66 slidably sealingly engaging the piston 73. The upper end of cylinder 72 in block 71 is recessed to receive one end of the barrel member 75 which has a recess 76, the same in diameter as cylinder 72 and forming the upper fluid displacement chamber of the double acting pump. The upper end of the barrel member 75 has a central opening through which the rod 77, attached to piston 73, passes.

The air motor portion of the unit 70 has a base block 81 which rests upon the pump block 71. A central "recess in motor block 81 contains a sealirig unit 82cm gaged by the end of barrel member 75 which extends into said recess in block 81. The piston rod 77 slidably ex-' tends through the sealing unit 82 and up into the air motor 80, which is of standard design and is operatively "connected to said piston rod 77, so that it reciprocat'es the rod when the motor is rendered active by the introduction of air pressure into the motor. Motor block 81 has a recess 83 in its end surface resting upon block 71. A radial bore 84 in the side of block 81 extends into the recess 83 and provides communication with an opening 85 in the side of barrel member 75, whereby the recess 83 is in communication with the upper displacement chamber 76 of the pump. The' outer end of the radial bore 84 is closed by a screw plug 86. An opening 87 in the wall of the barrel member 75, diametrically opposite opening 85 in said member, provides communication between the radial bore space 88 adjacent plug 86 and the upper displacement chamber 76 within barrel member 75. An opening 89 in the end surface of block 81 engaging block 71, communicates with space 88.

Two fluid passages 90 and 91 are provided in block 71 of the pump, said passages communicating at their lower ends respectively with passages 92 and 93 in block 41, and at their upper ends respectively with opening 89 and recess 83 in the motor block 81. The upper end of passage 90, communicating with opening 89, is of increased diameter to provide a seat for the ball check valve 94. A centrally orificed collar 95, set in a recess in the upper end surface of block 71, provides an abutment engaged by one end of spring 96, which engages valve 94 and yield ably urges said valve upon its seat in passage 90. Spring loaded valve 94 is the fluid inlet control valve for the upper fluid displacement pump chamber 76. A centrally orificed collar 97 is seated in the outer end of recess 83 in the motor block 81 and provides the seat for ball check valve 98 in the enlarged diameter end portion of passage '91. A spring 99 in said enlarged portion of passage 91, yieldably urges the ball check valve 98 upon its seat on collar 97. This valve 98 is the pressure outlet valve permitting the discharge of fluid under pressure from the pump displacement chamber 76.

The passage 92 in block 41, communicating With passage 90 in pump block 71, communicates with passage 100 in block 41, said passage 100 communicating with passage 52 in block 41, as shown in Figure 12, and in dotted lines in Figure 7. Thus, passages 53, 52, 100, 92, 90 including intake val-ve passages-94, 89, 88 and 84, form the intake passages for the fluid from the reservoir 44 to the fluid displacement chamber 76 at the upper end of the motor driven pump. From this chamber 76, fluid is discharged under pressure by piston 73, passing through opening 85 into recess 83, past fluid discharge valve 98 into passages 91, 93, 101 which, as shown inFigure 12, opens into passage 51, leading to the bottom end of the working cylinder 42. The outer end of the bore in block 41,. forming passage 101, shown in dotted lines in Figure 7, is closed by a plug.

The lower fluid displacement chamber 74 of the pump has valve controlled fluid passages communicating therewith, as shown in Figure 6. Block 41 has two recesses 105 and 106 in its upper surface engaged by the pump block 7 1. Recess 105 has a fluid passage 107 leading from the bottom thereof and communicating with passage 100, the outer end of which, terminating in the side of block 41, is closed by a plug. Recess 105 has a passage 108' leading from its side into the displacement chamber 74. A valve cage in recess 105 houses the fluid intake ball check valve 109, urged by spring 110 to shut off communication between passage 107 and recess 105. A passage 111 connects the displacement chamber 74 with recess 106, in which an orificed valve cage 112 provides a seat for fluid pressure discharge valve 113 which nor mally shuts otf communication between passagell'l and a'reduced diameter extension 114 of recess 106'. Recess portion 114, onthe exhaust sideof valve 113, connects 6 with passage 93 through passage 115, as shown in Figures 7 and 10. Passage 93, as-aforedescrib'e'd, connects with passage 101, which in turn connects with passage 51 leading into the work cylinder 42.

From the aforegoing, it may be seen that the fluid intake path for the lower displacement chamber 74 of the pump includes passage 53 from the fluid reservoir 44, passages 52, 100, 107, valve 109, passage 108 into chamber 74 as the piston 73 is moved upwardly by air motor 80. In response to downward movement of piston 73 by the air motor, fluid will be forced from displacement chamber 74 through passage 111, valve cage 112 in recess 106 past the discharge valve 113 into portion 114 of recess 106 (see Figures 6 and 10), passages 115, 93, 101 and51, which communicate with the bottom end of the working cylinder 42. Holes in block 41 receive bolts for securing the block 41 to thepump block 71. p The dotted line holes 121 in block 41 (see Figure 7) are threaded openings for receiving bolts to secure block 41 to the base 20. x

As heretofore mentioned, the double acting fluid pump and particularly the piston 73 thereof, is reciprocatively operated by the air motor 80 which may be of any desired standard make, the base block of which is designed and constructed as shown in section in Figure 5, so as to complement and complete the upper portion of the pump. A conduit 125 connects the air motor with the interior of the fluid reservoir 44 above the level of the fluid therein. This conduit 125 may be connected to any suitable source of air pressure 200, controlled by the hand valve 126.

The lifting jack of the present invention is provided with a hand operated unit for supplying fluid pressure to actuate the lifting unit in the event of air pressure failure or where no air pressure supply is available. This manually operated fluid pump unit is carried by the base 20' and consists. of a cylinder 131 screwed into recess 132 in block 41 (see Figures 1, 2, 3, 7, 8 and 9), A cylinder head cap 133 is provided at the outer end' of the cylinder 131, said cap having a central opening through which rod 134 slidably extends, the rod having a composite piston 135 attached at its inner end for reciprocation within said cylinder. Rod 134 is is secured to another rod 136 by a coupling 137. The rod 136 is anchored to a fulcrurned lever 138 pivotally se:

cured to a bracket 1'40 attached to the tubular member 43 of the workhig unit 40. The pivot pin supporting lever 138 is designated by the reference numeral 139 in Figures 2 and 3. An operating handle 141 is attached to lever 138.

As shown in Figure 3, the fluid intake and fluid discharge control valves for the hand operated pump 130 are housed within a valve cage 150. The Figures 4, 8 and 9 show the recess 1.32 in block 41 to have counterbored portions of different diameters, the outer portion being interiorly threaded to receive the" cylinder 131, the bottom and smallest counterbored portion provid ing an annular edge 151 forming a seat engaged by the chamtered inner annular edge of the valve cage (see Figure 4). The inner end of the valve cage 150 does not rest upon the bottom surface of recess 132, thus providing a space 152 from which a fluid passage 153 leads to connect with passage 154 which terminates in passage 51 (see Figure 9). Valve cage 150 has two fluid passages 155 and 156, the former passing completely through the valve cage and providing a .seat for the fluid pressure relief valve 157. Passage 156 termi nates short of the bottom end surface of the valve cage and provides a seat for the fluid intake valve 158. A portion of valve cage 150 is less, in outside diameter, than the inside diameter of the recess in the cylinder end into which the valve cage'extends, thus forming an annular space 160 between the valve cage and cylinder wall (see Figures 3 and 4). This space 160 isin cantmunication with a' passage 161 which cameos with passage 162 leading to and communicating with passage 52 connected with passages 53 to the fluid reservoir 44. The portion of recess 156 beneath the fluid intake valve 158 therein, is in communication with the annular space 160 through an opening 165 in the valve cage 150.

A fluid pressure relief valve is provided in the valve cage 150, which limits the fluid pressure delivered by the hand operated pump 130. This pressure limiting valve mechanism consists of a radial recess 170 in the valve cage terminating in another recess 1'71 opening in the end surface of the valve cage exposed to the fluid displacement chamber of cylinder 131. Recess 170 opens into the annular space 160. Recess 170 provides a seat for the pressure relief valve 175 urged upon the seat by spring 177, which engages the orificed plug 176 in the outer threaded end of recess 170.

Construction, relative arrangements and operational functions of the various elements of the lifting jack of the present invention are clearly set forth in the aforegoing description. Therefore, no further detailed operational description needs be made. However, identical operations in the raising of a load, for instance an automobile, will be given for a general understanding of the use of this device.

Assuming that the bumper, the bumper support or the frame of the automobile is to be engaged for lifting the vehicle, the saddle rests 35 are set transversely of the cross bar 33 of the lifting unit. The jack is then rolled into position, so that the saddle rests are directly beneath the vehicle bumper. The air pressure sup-ply line 200, including valve 126, is then connected with the conduit 125 and valve 126 is opened to direct air pressure to the air motor 80 and to the fluid reservoir 44, rendering the motor active for reciprocating the fluid pump piston 73. The air pressure upon the fluid is reservoir 44 forces the fluid from the reservoir through fluid passages, afore'described, into the working cylinder 42, causing the piston 48 therein and its rod 47 quickly and uninterruptedly to raise the lifting frame and its bracket 32, upon which saddle rests 35 are carried, to be moved into engagement with the vehicle bumper. This air pressure forced fluid will not raise the load; but merely actuate the jack quickly to engage the load. The air forced fluid will be directed to the displacement chambers of the fluid pump and thus supercharge them, assuring a complete filling thereof and thereby increasing the efliciency of the pump. While the air pressure fluid is raising the lifting frame to cause engagement of the saddle rests 35 with the load or vehicle bumper, pump piston 73 is active to deliver a fluid pressure impulse to the working cylinder 42 for each stroke of the piston 73. These fluid pressure impulses are effective to move the lifting frame of the jack and thus raise the load after the saddle rests 35 engage said bumper. When the load has been raised to the desired height, valve 126 is closed, to shut off the air pressure supply and thus the air motor is rendered inactive and, consequently, also the pump piston 73. Now the fluid is trapped within the working cylinder and the fluid passages leading thereto and consequently, the lifting rnembers of the jack, the piston 48, its rod 47 and the lifting frame and its bracket 32 are held in the raised position supporting the load in the lifted position. As a precautionary measure, a releasable safety latch 210 engages one of the apertures 212 in member 29 to positively hold the load in raised position. To lower the load, hand wheel 62 is actuated, to pennit the exhaust valve 59 (see Figure 16) to open and permit fluid from the cylinder 42 to return to the reservoir 44 under the influence of the load loaded piston 48 in said cylinder.

As soon as the jack supports the load or bumper of the vehicle, roller 22 of the jack yields, to permit the cross member 24 of the portable frame 20 to engage and rest upon the floor, thus eliminating the possibility of accidental rolling of the jack on the floor while the load is raised.

In case of a failure of the air pressure supply or where no air pressure is available, the jack cannot be power actuated. Under these circumstances, the hand pump must be operated to provide fluid pressure for actuating the lift. Hand lever 141 is raised and lowered to reciprocate the piston of the hand pump, thereby providing fluid pressure to the working cylinder 42 for raising the piston 48 therein and .thus raising the lift. Hand wheel 62 is operated to permit fluid in cylinder 42 to return to the reservoir and thereby permit the load to be lowered.

From the foregoing, it may be seen that the present invention provides a portable lifting jack that may be power or hand actuated to raise a load. If the lift is power or fluid pressure actuated, air pressure upon the fluid within the device causes the lift to be moved quickly and uninterruptedly into load engaging position, after which the power actuated means provides fluid pressure impulses to raise the lift with the load resting thereon. The air pressure upon the fluid causes the power actuated means to be supercharged, thereby assuring full efficiency in its operation. In case of a power failure, hand operated pressure producing means of the jack may be actuated to raise the lift in a manner similar to the power actuated means. Both the power lift and the hand lift may be used simultaneously, to thereby increase the speed at which the load is raised over the speed at which the load is raised by one lift operating alone.

The lifting jack is portable, that is, may be rolled upon the floor as long as no load is applied thereto. However, as soon as the load is encountered and lifting thereof is started, the jack is automatically brought into immovable contact with the floor, thereby preventing accidental rolling thereof while supporting a load.

Although the disclosure herein illustrates a vertical arrangement of the various cylinders, the cylinders need not be vertically positioned. The power lift may be used on service jacks that are rolled under the chassis of a motor vehicle. Furthermore, this power lift may be used on other types of lifts or hoists.

Although the preferred embodiment of the device has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode of operation, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

Having thus described my invention, 1 claim:

1. A load lifting jack consisting of a portable base; a block attached to the base and having a plurality of valve controlled fluid intake and discharge passages therein; a cylinder attached to the block and communicating with one of the fluid discharge passages therein, said cylinder containing a piston having a rod extending from the cylinder and adapted to engage and lift the load; a tubular member surrounding the cylinder and secured to the block, said tubular member forming an annular space about the cylinder providing a fluid reservoir in communication with a fluid intake passage in the block; a double acting fluid pump attached to the block, said pump having oppositely disposed chambers, each of the chambers of said pump communicating with said intake and said discharge valve controlled passages of said block; an air motor adapted to be connected to a source of air pressure for rendering said motor active, said motor being operatively connected with the fluid pump for actuating it; means connecting the air pressure line to the motor with the reservoir above the level of the fluid therein, said air pressure in the reservoir being operative to force fluid from the reservoir into the said cylinder for moving the piston rod into engagement with the load and into the displacement chamber of the pump for supercharging said chamber, and a manually operative fluid pump having a fluid displacement chamber with communicating valved fluid discharge and fluid intake passages, each of which communictes respectively with the cylinder and the reservoir and with corresponding valved passages leading to the respective displacement chambers of the power actuated pump, the fluid pressure upon the reservoir, the motor driven pump and the manually driven pump being adapted to operate simultaneously to raise the lift.

2. A load lifting jack consisting of a portable base, a block attached to the base and having a plurality of valve controlled fluid intake and discharge passages therein; a cylinder attached to the block and communicating with one of the fluid discharge passages therein, said cylinder containing a piston having a rod extending from the cylinder and adapted to engage and lift the load; a tubular member surrounding the cylinder and secured to the block, said tubular member forming an annular space about the cylinder providing a fluid reservoir in communication with the fluid intake passage of the block,

the wall of the cylinder being provided with two pressure relief orifices, one nearer the top of the cylinder than the other, both providing communication between the reservoir and the intake of the cylinder above the piston, the orifice more remote from the cylinder top providing communication between the reservoir and the displacement chamber beneath the piston when said piston has reached its highest piston extending position within the cylinder, a double acting fluid pump attached to the block, said pump having oppositely disposed chambers, each of the chambers of said pump communicating with said intake and said discharge valve controlled passages of said block, an air motor adapted to be connected to a source of air pressure for rendering said motor active, said motor being operatively connected with the fluid pump for actuating it; means connecting the air pressure line to the motor with the reservoir above the level of the fluid therein, said air pressure in the reservoir being operative to force fluid from the reservoir into the said cylinder for moving the piston rod into engagement with the load and into the displacement chamber of the pump for supercharging said chamber, and a manually operative fluid pump having a fluid displacement chamber with communicating valved fluid discharge and fluid intake passages, each of which communicates respectively with the cylinder and the reservoir and with corresponding valved passages leading to the respective displacement chambers of the power actuated pump, the fluid pressure upon the reservoir, the motor driven pump and the manually driven pump being adapted to operative simultaneously to raise the lift.

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